Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance

On Wed, Jan 15, 2014 at 2:52 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> I think that the bottom line is that we're not likely to make massive
>> changes to the way that we do block caching now.  Even if some other
>> scheme could work much better on Linux (and so far I'm unconvinced
>> that any of the proposals made here would in fact work much better),
>> we aim to be portable to Windows as well as other UNIX-like systems
>> (BSD, Solaris, etc.).  So using completely Linux-specific technology
>> in an overhaul of our block cache seems to me to have no future.
>
> Unfortunately, I have to agree with this.  Even if there were a way to
> merge our internal buffers with the kernel's, it would surely be far
> too invasive to coexist with buffer management that'd still work on
> more traditional platforms.
>
> But we could add hint calls, or modify the I/O calls we use, and that
> ought to be a reasonably localized change.


That's what's pretty nice with the zero-copy read idea. It's almost
transparent. You read to a page-aligned address, and it works. The
only code change would be enabling zero-copy reads, which I'm not sure
will be low-overhead enough to leave enabled by default.